Variable volume air conditioning system with velocity readout at the thermostat

Abstract

A variable volume air conditioning system of the type having a duct for distributing air to a room, a damper for regulating the flow of air through the duct, and a damper actuator responsive to damper drive control signals for controlling the damper. A thermostat located in the room provides a stat signal representative of a desired flow of air through the duct. An actual flow signal representative of the actual flow of air through the duct is provided by a sensor. The stat signal and actual flow signal are compared by a comparator which provides the damper drive control signals as a function of the comparison. A wire transmission line couples the actual flow signal from the sensor to the thermostat so that service personnel can easily monitor system performance.

What is claimed is: 
     
       1. For use in conjunction with an air distribution system of the type having a duct for distributing air to a room, a damper for regulating the flow of air through the duct, and a damper actuator responsive to damper drive control signals for controlling the damper, a circuit for providing the damper drive control signals, including: stat means to be positioned in the room for providing a stat signal representative of a desired flow of air through the duct;   sensor means for sensing the flow of air and for and for providing an actual flow signal representative of the actual instantaneous flow of air through the duct;   control means responsive to the stat means and the sensor means for providing damper drive control signals as a function of the stat signal and the actual flow signal; and   transmission means having a first end coupled to the sensor means and a second end coupled to the stat means for providing the actual flow signal to the room.   
     
     
       2. The circuit of claim 1 wherein the stat means includes display means coupled to the second end of the transmission means for providing a visual display of the actual air flow. 
     
     
       3. The circuit of claim 1 wherein: the sensor means includes means for providing an electric actual flow signal representative of the actual flow of air through the duct; and   the transmission means includes a wire having a first en coupled to the sensor means and a second end terminating at a terminal in the stat means.   
     
     
       4. The circuit of claim 1 wherein the sensor means includes: controlled signal source means for providing an actual flow signal representative of the actual flow of air through the duct as a function of a balance state signal;   temperature sensitive bridge means, at least partially exposed to the flow of air in the duct, having an input port connected to receive the actual flow signal from the controlled signal source and an output port at which an output signal is provided as a function of the flow of air impinging upon the exposed portion of the bridge and the actual flow signal; and   balance sensing circuit means coupled to receive the output signal from the output port of the bridge, for providing the balance state signal to the controlled signal source as a function of the balance state of the bridge, wherein the bridge will be in a balanced state when the actual flow of air equals the desired flow of air.   
     
     
       5. The circuit of claim 1 wherein the stat means includes temperature set means for providing the stat signal as a function of actual temperature within the room and a desired temperature within a room. 
     
     
       6. The circuit of claim 1 wherein: the stat means provides a stat signal having a first range representative of a desired range of flow of air thorugh the duct;   the sensor means provides an actual flow signal having a second range representative of an actual range of flow of air through the duct; and   the system further includes a signal divider means coupled between the sensor means and the control means for translating the actual flow signal to the first range representative of the actual flow of air through the duct.   
     
     
       7. The circuit of claim 1 wherein the control means includes a comparator for comparing the actual flow signal to the stat signal and for providing the damper drive control signals as a function of the comparison. 
     
     
       8. A variable volume air conditioning system for supplying air to a room, including: a conditioned air supply;   a duct for distributing conditioned air from the contitioned air supply to the room;   a damper positoned in the duct for regulating flow of air into the room;   damper actuator means responsive to damper drive control signals for controlling the damper;   thermostat means positioned at an accessible location within the room for providing a stat signal representative of a desired air flow;   sensor means positioned with respect to the duct for sensing the flow of air and for providing an actual flow signal representative of actual instantaneous flow of air through the duct;   control means responsive to the thermostat means and the sensor means for providing the damper drive control signals as a function of the stat signal and the actual flow signal; and   transmission means having a first end coupled to the sensor means and a second end coupled to the thermostat means for providing the actual flow signal to the thermostat means.   
     
     
       9. The air conditioning system of claim 8 and further including display means coupled to the second end of the transmission means for providing a visual display of the actual air flow. 
     
     
       10. The circuit of claim 8 wherein: the sensor means includes means for providing an electric actual flow signal representative of the actual flow of air through the duct; and   the transmission means includes a wire having a first end coupled to the sensor means and a second end coupled to the thermostat means.   
     
     
       11. The air conditioning system of claim 8 wherein the sensor means includes: controlled signal source means for providing an actual flow signal representative of the actual flow of air through the duct as a function of a balance state signal;   temperature sensitive bridge means, at least partially exposed to the flow of air in the duct, having an input port connected to receive the actual flow signal from the controlled signal source and an outup port at which an output signal is provided as a function of the flow of air impinging upon the exposed portion of the bridge and the actual flow signal;   balance sensing circuit means coupled to receive the output signal from the output port of the bridge, for providing the balance state signal to the controlled signal source as a function of the balance state of the bridge, wherein the bridge will be in a balanced state when the actual flow of air equals the desired flow of air.   
     
     
       12. The air conditioning system of claim 8 wherein the thermostat means includes temperature set means for providing the stat signal as a function of actual temperature within the room and desired temperature within the room. 
     
     
       13. The circuit of claim 8 wherein: the thermostat means provides a stat signal having a first range representative of a desired range of flow of air through the duct;   the sensor means provides an actual flow signal having a second range representative of an actual range of flow of air through the duct; and   the system further includes signal divider means coupled between the sensor means and the control means for translating the actual flow signal to a first range representative of the actual flow of air through the duct.   
     
     
       14. The air conditioning system of claim 8 wherein the control means includes a comparator for comparing the actual flow signal to the stat signal and for providing the damper drive control signals as a function of comparison. 
     
     
       15. The air conditioning system of claim 8 wherein the damper actuator means includes a motor.